Optical sensitization of direct positive emulsions



March 29, 1960 M. COENEN ETAL 2,930,594

OPTICAL SENSITIZATION OF DIRECT POSITIVE EMULSIONS Filed March 12, 1957 F/G.5 N

IN V EN TORS MAX COENEN JOHANNES GOETZE ULRICH GRISAR, OSKAR RIESTER, WERNER STRZCKE, KARL Z/E TAN. BY a *3? "1747 A TTORNEYS United States OPTICAL SENSITIZATION F DIRECT POSIT EMULSIONS Application March 12, 1957, Serial No. 645,544 Claims priority, application Germany March 19, 1956 11 Claims. c1. 96-400 The present invention relates to the sensitizing of direct positive photographic silver salt emulsions. A very large number of dyes have already been proposed for sensitizing silver halide emulsions, many of these dyes originating from the class comprising the polymethine dyes. Nevertheless, this class includeswhole groups which have no sensitizing ability or which even have a desensitizing efiect. The number of sensitizers which can be used in practice is further restricted by the fact that there is a large num ber of other requirements concerning the way in which the sensitizer operates when incorporated into silver halide emulsion layers. For example, the clearness of the layers and of the images produced therein must not be reduced and stability on storage, particularly as regards freedom from fogging and intensity of sensitization, must be guaranteed. Furthermore, the gradation in both the fresh and in the aged condition must have the required value and must not change. 1

For the purposes of color photography, it is onlypossible to use those sensitizers meeting these requirements which in addition have a particularly high sensitizing action and also a special selectivity. It is even necessary to have a quite specific spectral sensitivity distribution for obtaining the best possible color reproduction. It is obvious that all these requirements can be more or less com.- pletely met only by relatively few dyestuffs.

-In the modern color photographic processes, the color couplers may be present in the emulsion and these in many cases impair the sensitizing action, whereby the number of dyes which can be used is still further reduced.-

The case is particularly complicated when the silverhalide emulsions used are those which show the solarization effect, that is to say produce a direct positive silver, image when exposed to the object to be reproduced and then developed in a silver halide developing solution. It has actually been found that with direct positive; emulsions containing color formers the sensitizers which have formerly been proposed for color photography can be used with only slight success or cannotbe used at all.

' It has now been found that bis-(1-alkyl-2-phenyl-indole-' 3)-trimethine cyanines of the general formula l X- N I H i in which U atent" III 2,930,694 Patented Mar. 29 1960 or a halogen atom, such as chlorine, bromine, iodine, and I R" is a hydrogen atom or an alkyl such as methyl, ethyl,

propyl, butyl, cycloalkyl, such as cyclohexyl, cyclopentyl, thienyl or RC H radical,

X is an anion, such as 01-, Br, I-, 010,-, cn so em -so,-

II i

C H-C H=CH CaHs H509 l CH3 It is further found that the introduction of the phenyl nuclei has an extremely favorable influence on the sensitizing eifect with respect to direct positive emulsions.

Fig. 1 shows the sensitization of dye II, and Fig. 2 that of dye III.

It will be seen from these two examples that valuablepanchromatic sensitizers I for direct positive "silver salt emulsions are made available by using bis-(1-alkyl-2-' phenyl-indole-3)-trimethine cyanines.

It is a surprising fact that the introduction of further' substituents, whether these be alkyl or alkoxy groups or halogen atoms, into the benzene ring of the indole does not produce any improvement in the sensitization, as is clear from Fig. 3, which shows the sensitization of dye IV.

On the other hand, the introduction of alkyl or alkoxy groups into the phenyl radicals causes a further substantial improvement in the intensity of the sensitization.

Fig. 4 shows the sensitization curve of dye V The increase in sensitivity of a direct positive emulsion sensitized with dye V and containing a coupler such 1 hydroxy 2-naphthoyl amino-4'-methyloctadodecylaminoa: henzene-3',-sulfonic acid for the production of a; cy ar 1; color image by the process of color forming development;

- is.up to 6 Scheiner as compared with the sensitivityci v cam H CH: I on:

. -OCH: CHaO- 3 an=emulsion-sensitized with dye- III. Dye VI yields practically the same result.

The favorable influence of methyl groups on the 2- phenyl radicals is indicated by Fig. 5 which shows the sensitivity of dye VII.

"H-CII -CH e ZHs CH9 CH3 CH3- acsaaaa- The alkyl or alkoxy groups or the halogen atoms can however also be introduced into other positions of the 2 phenyl nuclei, for example in the ortho position, a shown for examplein dye VIIa.

VIIa

An even more extensive deepening of the color, and thus a displacement of the sensitization maximum towards longer waves, is caused by the introduction of a thiophene radical into the OL-POSitiOl] of the trimethine chain.

Dye VIII absorbs at-645 m the sensitization maximum is at 670-680 111,14, and dye IX absorbs at 650 mu.

VIII

CH "H i OlOr /L T ens OCH3 C1- 0 OH OH 1 0 Q C104 f/ CH; CH:

1 OCH; 01-1 0 ment; Such couplers are for instance disclosed in-US.

patent specifications 2,179,234, 2,186,849, 2,265,547,

The dyestufis illustrated in the above formulae were dissolved in methanol and added to a direct positive emulsion in quantities of-60 mg. per -1 kg. of emulsion. To the sensitized emulsion there were added 10 g. of the sodium salt of sulfonated 1-hydroxy-2-naphthoic acid octadecylamide in the form of a methanolic solution.

When the dyes are dyes which arelnot substituted in the methine chain, they are produced either by known processes, for example according to W. Konig, J.pr.Ch. (2), 84, page 216; (2),, 87, page 241; Brooker, J. Amer. Chem. Soc. 62 (1940), page 1116, by reacting the corresponding indoles with fi-ethoxyacrolein acetal, or, if they are unsymmetrical dyes of the type V, VI, VIII, or IX, by reacting ketones,for example of the formulae- CHa such as -can.-be obtained for example according to German patent specification No. 614,326, with Grignard compounds to convert them into ethylenes with S-formyl indoles, I unsubstituted indoles according to Vilsrneyer, [Berichte der Deutschen Chemischen Gesellschaft, vol. 60 (.1927),-

page 121] these ethylenes yield the -desired dyestuif, for example:

mineral acids.

The following details are given concerning the production-of the above dyestufis:

1935, page 1210, are heated on a vapor bath until com.- plete dissolution has occurred. 1 gram of fl-ethoxy acrolein acetal and 0.8 cc. of hydrobromic acid are added to the hot solution, which is then allowed to cool. .After 5 hours, the precipitated dyestuflf'is filtered oif. with.'suc.- tionfand recrystallized from methanol. The absorption maximumof the "dye's'tuifin alcoholic solution "is 596 which can-be obtained from .3-

in glacial acetic acid solution and in the presence of assess;

(2) DYESTUFF OF THE FORMULA III Bis-(1-methyl-2-phenylindolyl-3)-a-phenyl trimethz'ne cyanine perchlorate (a) l-methyl-2-phenyl-3-benzoyl-indole: 21 grams of 1-methyl-2-phenylindole, 20 grams of benzanilide, and 46 grams of phosphoric oxachloride "and is filtered off with suction and recrystallized from methanol. The yield is 15 grams, the melting point is 123 C.

' (b) Asym.-(1-methyl-2-phenyl-3-benzoylindole) phenylethylene:

A suspension of 6 grams of 1-methyl-2-phenylindolyl-3 in 30 cc. of benzene is added in small portions to a Grignard solution of 1.5 grams of magnesium, 4 cc. of methyl-iodide and 30 cc. of ether. The mixture is slightly boiled for 2 hours and then mixed with iced water and sulphuric acid. The ether-benzene layer is separated, dried and evaporated. Two grams of a light brown powder are left behind.

(c) Dyestufi formation:

1.5 grams of the ethylene described under (b) and 1.1 grams of 1-methyl-2-phenyl-3-formylindole, described in Journ. of Org. Chemistry, volume 10, page 255 (1945), are dissolved in 15 cc. of hot glacial acetic acid. 0.4 cc. of hydrobromic acid is added and the mixture is allowed to cool. After 4 hours, 0.5 cc. of perchloric acid dissolved in 5 cc. of methanol is added, the mixture is left standing for some hours and the dyestnlf perchlorate is filtered off with suction. The filtration residue is alternately washed with methyl and benzene until the lighter soluble red byproduct is separated. Then the dyestuff is recrystallized from methanol. The absorption maximum of the dyestuif in methanolic solution is 615 mp (3) DYESTUFF OF THE FORMULA V Bis- [I -methyl-2-(p-methoxy-phenyl -indolyl-3 x-phenyltrimethine cyanine perchlorate (a) l-methyl 2 p-methoxy-phenyl-3-benzoyl-indole: 72 grams of 1-methyl-2-p-methoxy-phenyl-indole (boiling point 204-208 C. at 2 mm. Hg, prepared from the n-methyl-phenyl-hydrazone of p-methoxy acetophenone by melting with zinc chloride at 180 C), 60 grams of benzanilide and 135 grams of phosphoric oxychloride are heated to 105 C. for 5 hours. The melt is then decomposed by boiling with 3 litres of hydrochloric acid for 2 hours and immediately poured onto ice. The precipitated mass is filtered ed with suction, covered with ethanol and filtered off once more with suction after 12 hours. The residue can be recrystallized from about 1 litre of ethanol. 62 grams of ketone of the melting point 134 C. are obtained.

.(b) Asym. [1 methyl 2 indolyl-3]-phenyl-ethylene:

A solution of grams of ketone (a) in 100 cc. benzene is slowly added to a Grignard solution of 6.6 grams of magnesium, 20 cc. of iodomethane and 140 cc. of ether. After the addition is finished, the mixture is heated for 2 hours, then decomposed with ice and sulphuric acid, and the ether-benzene layer is separated. The ether and benzene are substantially evaporated and the ethylene is precipitated with methanol. Melting point at 158 C.

(c) l-methyl 2 p-methoxy-phenyl-3-formyl-indole:

7 grams of N-methyl-formyl-aniline and 7.7 grams of phosphoric oxychloride are left standing at room temperature while stirring for 2 hours. The mixture is then p-m ethoxy-phenyl) mixed with grams of ordichloro-benzene and 11.8 grams of 1'methyl-Z-p-methoxy-phenyl-indole are introduced at C. The mixture is left standing for 20 hours and then decomposed with 50 grams of ice and 40 grams of concentrated sodium hydroxide solution while cooling. The dichlorobenzene is distilled off in vacuum and the residue is recrystallized from methanol. Melting point 142 C.

(d) Dyestuif formation:

10.2 grams of the asym. ethylene compound (described under (12)) and 8.5 grams of the formyl compound (described under (c) are dissolved in 100 cc. of hot glacial acetic acid, 3 cc. of hydrobromic acid are added, and the mixture is left standing at room temperature for 5 hours. 4 cc. of perchloric acid dissolved in 40 cc. of methanol are added and the dyestuif perchlorate can be filtered off after a further 4 hours. The dyestutf is alternately washed with methanol and benzene several times and then recrystallized from about 3 litres of methanol to which 2 cc. of hydrobromic acid were added. The absorptionmaxirnum of the dyestuif in methanolic solution is 625 (4) DYESTUFF OF THE FORMULA VI (1 methyl 2 phenylindolyl 3)[1 methyl-2'-(pmethoxy-phenyl) indolyl 3l-a-(p-methoxy phenyl)-trimethine cyanin'e perchlorate (a) l-methyl 2 Q phenyl-3-p-methoxy-benzoyl-indole:

21 grams of 1-methyl-2-phenyl-indole, 24 grams of p-methoxy-benzanilide and 45 grams of phosphoric oxychloride are treated at -105 C. for 5 hours.- The reaction mixture is then boiled with 1 litre of 15 hydrochloric acid for 2 hours, poured onto ice and the semi-solid mass is separated by grinding the mass with little ethanol, solidification occurring soon. 20 grams of ketone of the melting point 112 C. are obtained.

-(b) Asym.-(1-methyl-2-phenyl-indolyl 3-(pmethoxyphenyl) )-ethylene:

17 grams of the ketone described in the preceding paragraph dissolved in 60 cc. benzene are added dropwise to a Grignard solution of 3.8 grams of magnesium, 11.4 cc. of iodomethane and 100 cc. of ether. After the reaction is complete, the mixture is kept at boiling temperature for another 2 hours, then decomposed with ice and sulphuric acid, and the ether-benzene mixture is separated off. After drying with sodium sulphate, the solvents are substantially evaporated and the ethylene precipitates with methanol. Yield: 5 grams, melting point 131 C.

(0) Dyestufi formation:

1.5 grams of the asym. ethylene obtained as described in the preceding paragraph, and 1.3 grams of l-methyl- Z-(p-methoxy-phenyl)-3-formyl indole, which is obtained as described in Example 3(c), are dissolved in 14 cc. of hot glacial acetic acid. 0.5 cc. of hydrobromic acid is added and the solution is left standing for 4 hours. After adding 0.3 cc. of perchloric acid dissolved in 5 cc. of methanol, the perchlorate of the dyestutr' precipitates. The precipitate is filtered off with suction after some hours, alternately washed with methanol and benzene several times, and finally recrystallized from methanol.

The absorption maximum in methanolic solution is 625 mu.

(5) DYESTUFF OF THE FORMULA VII concentrated hydrobromic acid are added to the hot solu-.

tion, which is then left standing for 14 hours. During that time crystals precipitate which are filtered off with suction, washed with benzene and little methanol and then recrystallized from methanol.

(6) DYESTUFF OF THE FORMUIQA VIII 1--methyZ-Z-(p-methoxy phenyD-indolyld]-[1'- methyl- 2 (p-chlorophenyl) indolyl 3'] a (wthienyD-trimethine cyanine perchlorate are heated to 105 C. for hours. The melt is introduced' into hot dilute hydrochloric acid and the mixture is heated to boiling temperature for 2 hours. Thereupon the mixture is poured into ice water, the precipitate formed is filtered off with suction and recrystallized from ethanol. Yield: 7 grams, melting point 140 C.

(h) Asym.-[l-methyl2-(p methoxyphenyl) -indolyl- 3]-a-thienyl-e'thylene:

7 grams of ketone obtained as described in the preceding paragraph dissolved in cc. of benzene are added to a Grignard solution of 1.4 grams of magnesium, 30 cc. of ether and 4 cc. of iodo-methane. After boiling for 2 hours, the mixture is decomposed with ice,

acidified with sulphuric'acid, the benzene and ether layer is separated, washed and dried. After evaporating the benzene, 5 grams of ethylene of the melting point 115 Care obtained.

I (c) 1-methyl-2-(p-chlorophenyl)-3-formyl-indole:

7 grams of N-methyl-formyl-aniline are stirred with 7.7 grams of phosphoric oxychloride at room temperature for 2 hours. The mixture is diluted with 40 cc. of o-dichlorobenzene and 12 grams of l-methyl-Z-(p-chlorm phenyl)-indole are introduced at 5l0 C. The mixture is then left standing for 20 hours, rendered alkaline with concentrated sodium hydroxide solution and ice (the temperature must not rise above 15 C.), the dichlorobenzene is separated, washed neutral, dried and distilled off in vacuum. The residue can be recrystallized from methanol. Yield: 10 grams, melting point 134? C.

(d) Dyestuff formation:

1 1.7,grams of the ethylene described in 6(b) and 1.35 grams of the aldehyde obtained as described in 6(c) are dissolved in 15 cc. of hot glacial acetic acid. 0.5 cc. of concentrated hydrobromic acid are added to the solution. Formation of the dyestufl starts. at once. After 5 hours, 0.5 cc. of perchloric acid dissolved in 50 cc. of methanol is added. After 14 hours, some methanol is added and the precipitated crystals (starting products). are filtered 01f with suction. Another quantity of 1 cc. of perchloric acid is added to the filtrate, the mixture is then left standing for one day and the resultingprecipitate is filtered off again with suction. The residue is washed with much benzene and much alcohol until the efiiuent no longer shows a red coloration. The-residue on the; filter is recrystallized from methanol. The pure dyestuif has an absorption maximum in methanolic solution of 645 my. and a sensitization maximum of 670 m (7 DYESTUFF OF THE FORMULA VIIa Bis- [1-methyl-2-(o-methyl-phenyl) -indolyl3 -trimethine cyanine perchlorate 2 grams of l-r'nethyl-Z- o-methyl-phenyl -indole, cc. of absolute alcohol,

1 ,cc. ofethoxy acrolein acetal, and

0.8 cc. ofconcentrated hydrochloric acid are briefly heated on the vapor bath and thenleft standing for 12 hours. 20 cc. of alcohol and 0.5 cc. of perchloric acid. are. added, whereupon the dyestuffprecipitates. immediately. The dyestutf'is recrystallized from methanol.

--sa (8) DYESTUFF OF THE FORMULA IX Bis-[1-methyl-2-(p-meth0xy-phenyl)-ind0lyl-3]-a-(athienyl)-trimethine cyanine perchlorate 2.5 grams asym.-[l-methyl-2-(p-methoxy-phenyl)-indolyl-3l-a-thienyl ethylene, as described in Example 6(b) and 1.9 grams of l-methyl-2-p-methoxy-phenyl-3 formylindole as described in Example 3(a), are dissolved in 30 cc. of hot glacial acetic acid, 0.7 cc. of hydrobromic acid is added and the mixture is left standing for 6 hours. 1 cc. of perchloric acid dissolved in 10 cc. of methanol is added and the dyestuff formed is filtered off with suction after standing several hours. The dyestufi is washed with benzene and methanol in the usual manner until the eflluent no longer shows a red coloration and the dyestuff is then recrystallized from methanol. ti on maximum of the dyestuif in methanolic solution is 650 [Ii 1..

Suitable direct positive emulsions are disclosed in the patent specification of German Patents No. 606,392, 642,222, 693,917 and 749,864.

We claim:

1. A photographic material comprising a direct positive silver halide emulsion layer containing at least one in. which:

R is an alkyl radical,

R is a member'of the group consisting of a hydrogen atom, an alkyl radical, an alkoxy radical, and a halogen atom,

R" is a member of the group consisting of a hydrogen atom, an alkyl, cycloalkyl, thienyl, and RC H radical,

R is a member of the class consisting of a hydrogen atom and a methoxy radical, and

X stands for an anion.

2. A photographic material comprising a direct positive silver halide emulsion layer containing a color coupler capable of reacting with the oxidation product of a primary aromatic amino developing agent to form a dye,- and also containing at least one optical sensitizer of the general formula:

R is' a member of the group consisting of a hydrogen atom, an alkyl radical, an alkoxy radical, and a halogen atom,

R is a member of the group consisting of a hydrogen atom; an alkyl, cycloalkyl, thienyl, and R-C ;H -v radical,

R is a'member of the class consisting of a hydrogen atom. and amethoxy radical, and

XI'stands for an anion.

3. A photographic. material comprising a direct posi- The absorp tive silver halide emulsion layer containing at least one optical sensitizer of the general formula:

CH-CH=CH I Br- N CaH5 HrCo N CH3 CH3 4. A photographic material comprising a direct positive silver halide emulsion layer containing at least one optical sensitizer of the general formula:

(1111; CH: 5. A photographic material comprising a direct positive silver halide emulsion layer containing at least one optical sensitizer of the general formula:

H: CH:

6. A photographic material comprising a direct positive silver halide emulsion layer containing at least one optical sensitizer of the general formula:

H; H H 0 IL L L 0 l C I i N CHI A 0 OH: CHsO 7. A photographic material comprising a direct positive silver halide emulsion layer containing at least one optical sensitizer of the general formula:

OCH:

23H: CH.

CHsO

8. A photographic material comprising a dired; positive silver halide emulsion layer containing at least one optical sensitizer of the general formula:

OCH: CH:

9. A photographic material comprising a direct positive silver halide emulsion layer containing at least one optical sensitizer of the general formula:

CHI-C H=CH CH: CH:

10. A photographic material comprising a direct positive silver halide emulsion layer containing at least one optical sensitizer of the general formula:

11. A photographic material comprising a direct positive silver halide emulsion layer containing at least one optical sensitizer of the general formula:

OTHER REFERENCES Mees: The Theory of the Photographic Process," pages 379 to 391 relied upon (1954); The Macmillan Co., publishers, New York, N.Y. (Copy in Sci. Library.) 

1. A PHOTOGRAPHIC MATERIAL COMPRISING A DIRECT POSITIVE SILVER HALIDE EMULSION LAYER CONTAINING AT LEAST ONE OPTICAL SENSITIZER OF THE GENERAL FROMULA: 